Beyond brewing: β-acid rich hop extract in the development of a multifunctional polylactic acid-based food packaging

Synthesis of β-acids loaded chitosan-sodium tripolyphosphate nanoparticle towards controlled release, antibacterial and anticancer activity

The development of nanoparticles loaded with natural active ingredients is one of the hot trends in the pharmaceutical industry. Herein, chitosan was selected as the base material, and sodium tripolyphosphate was chosen as the cross-linking agent. Chitosan nanoparticles loaded with β-acids from hops were prepared by the ionic cross-linking method. The results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that chitosan nanoparticles successfully encapsulated β-acids. The loading capacity of chitosan nanoparticles with β-acids was 2.00 %-18.26 %, and the encapsulation efficiency was 0.58 %-55.94 %. Scanning electron microscopy (SEM), transmission electron microscope (TEM), particle size, and zeta potential results displayed that the nanoparticles revealed a sphere-like distribution with a particle size range of 241-261 nm, and the potential exhibited positive potential (+14.47-+16.27 mV). The chitosan nanoparticles could slowly release β-acids from different simulated release media. Notably, the β-acids-loaded nanoparticles significantly inhibited Staphylococcus aureus ATCC25923 (S. aureus) and Escherichia coli ATCC25922 (E. coli). Besides, β-acids-loaded chitosan nanoparticles were cytotoxic to colorectal cancer cells (HT-29 and HCT-116). Therefore, applying chitosan nanoparticles can further expand the application of β-acids in biomedical fields.

Facile green synthesis of wasted hop-based zinc oxide nanozymes as peroxidase-like catalysts for colorimetric analysis

Hops are a common ingredient in beer production, and a considerable quantity of hops is usually discarded as a waste material once the brewing process is completed. Transforming this waste material into valuable nanomaterials offers a sustainable approach that has the potential to significantly mitigate environmental impact. Herein, a facile and green protocol for the production of zinc oxide nanozymes (ZnO NZs) using wasted hop extract (WHE) as a natural precursor was demonstrated. The process involved a hydrothermal synthesis method followed by a calcination step to form the final ZnO NZs. The results revealed that lupulon, the main β-acid in hops, particularly the phenolic hydroxy group, is primarily responsible for the biosynthesis of ZnO NZs. The WHE-ZnO NZs exhibited exceptional peroxidase-like (POD-like) activity and served as effective catalysts for the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). Analysis of the catalytic mechanism revealed that the POD-like activity of these WHE-ZnO NZs originated from their ability to expedite the transfer of electrons between TMB and H2O2, resulting in the enzymatic kinetics following the standard Michaelis-Menten mechanism. Furthermore, we developed a straightforward and user-friendly colorimetric technique for detecting both H2O2 and glucose. By utilizing the WHE-ZnO NZs as POD-like catalysts, we achieved a linear detection range of 1-1000 μM and a limit of detection of 0.24 μM (S/N = 3) for H2O2 detection and a linear range of 0-100 mM and a detection limit of 16.73 μM (S/N = 3) for glucose detection. These results highlighted the potential applications of our waste-to-resource approach for nanozyme synthesis in the field of analytical chemistry.